Late Thursday evening, the Trump Administration launched dozens of Tomahawk missiles at Syrian targets in response to a chemical attack that killed civilians earlier this week. Trump reportedly did not receive Congressional approval for the attacks, raising questions about the constitutionality of the military strike.

Under the 2001 Authorization for Use of Military Force, which was passed just after the Sept. 11 attacks on the World Trade Center, the president is authorized to "use all necessary and appropriate force" to prevent future terror attacks against the United States. While this legislation specifically referred to terrorist groups involved in the Sept. 11 attacks, it can arguably be applied to ISIS because the terror group split off from al Qaeda.

But many politicians are not convinced that this can be used as a justification for Trump's launching airstrikes in Syria without Congressional approval. Republican Senator Rand Paul of Kentucky has been one of the most vocal conservative opponents of the president, expressing concern about airstrikes as soon as Trump proposed them on Thursday afternoon.

"The president needs congressional authorization for military action as required by the Constitution, and I call on him to come to Congress for a proper debate. Our prior interventions in this region have done nothing to make us safer, and Syria will be no different," Paul said.

Paul, and several other lawmakers, say that Trump's actions in Syria are not constitutional because the United States has not been attacked by the Syrian regime. They argue that an act of aggression against Assad is an act of war that must receive congressional approval.

Trump himself once agreed with them. In 2013, when President Barack Obama deliberated over whether to use military force in Syria after the Assad regime killed over 1,000 people in the worst chemical attack in the country's six-year civil war, Trump tweeted his opposition. Now, just two days after a similar attack against Syrian civilians, Trump has taken swift action.

Some Republican senators, like John McCain of Arizona, are defending Trump's choice, stating that the horrendous chemical attacks justify U.S. intervention. Speaker of the House Paul Ryan considers the strikes a valuable first step in holding Syrian President Bashar al-Assad accountable for his alleged human rights abuses.

The military action seems to signify a shift from the Trump Administration's new policy of focusing on developing a military strategy to defeat ISIS instead of trying to remove Assad from power.

"I think what Assad did is terrible. I think what happened in Syria is one of the truly egregious crimes. It shouldn't have happened. It shouldn't be allowed to happen," Trump told reporters early Thursday. "I think what happened in Syria is a disgrace to humanity."

According to the New York Times, Secretary of State Rex Tillerson is scheduled to meet with Russian leaders in Moscow next week. Russia has been a key ally for Assad throughout the Syrian Civil War, and the U.S. airstrikes may be used as a bargaining chip for Tillerson to persuade the country to keep Assad in check.